The availability of relatively small turbofan engines for use in aviation resulted in the development of small jet aircraft. Because these aircraft are so light, they can use purely mechanical linkages (e.g., cables, push-pull rods etc.) for operating in-flight control devices such as ailerons, elevators, and rudders. Normally, an aircraft rudder is controlled by foot pedals and the pilot displaces either the right or left pedal to yaw the aircraft to the right or left respectively.
Jet aircraft also need to have a nose wheel steering system for control of the aircraft while on the ground. It is desirable to use the same foot pedals to control the rudder in flight and the nose wheel on the ground. However, the nose wheel steering may be operated by a fluid power system as part of a ‘steer by wire’ system.
Since the same foot pedals are used for both in flight and on the ground control of the aircraft, it is important that nose wheel steering is enabled only when the aircraft is on the ground as sensed for, by example, a switch actuated when the weight of the aircraft is carried by the landing gear.
When the nose wheel steering system is enabled, the pilot may displace either pedal to turn the nose wheel in the respective direction. The pedal displacement generates an electrical signal that actuates a fluid cylinder to turn the nose wheel and steer the aircraft to the right or left. One potential problem with a steer by wire system is that the nose wheel may not automatically return to a “centered” position after the pilot releases a foot pedal.
Therefore, there exists a need in the art for an aircraft nose wheel steer by wire steering system in which the nose wheel is automatically returned to a centered position when the pilot releases the foot pedals and in which biasing forces applied to center the nose wheel are not applied when in flight.